Because of a desire to reduce power consumed by modern devices, maximum operating voltages of electronic devices have been decreasing over time. Several years ago common operating voltages for circuits were in the range of 5 volts or more, such as for TTL (Transistor-to-Transistor Logic) circuits. But more recently, the minimum power supply operating voltage for newer electronic devices may be much lower, e.g., in the range of 900 mVolts.
A problem arises when modern circuits are mated with legacy components in a single device, such as in a typical computer system. For instance, a hard disk controller may operate at 900 mVolts, but the disk drive that it is controlling may be older and continue to operate from a 5 volt power supply. One reason for the supply voltage mismatch is that not all components of a computer system are simultaneously updated.
A problem exists because a standard power supply for a particular device may provide a supply voltage that is too high or too low for interoperability with other components in the same system. Exposing a circuit to a voltage higher than it is designed for may electrically or physically compromise the circuit. Driving a circuit at a voltage lower than it is designed for may cause data errors, because data signal levels are not high enough to be detected. Either condition is problematic.
Embodiments of the invention address this and other limitations of the prior art.